1. Field of the Invention
The present invention relates to a light emitting device (LED) driving apparatus that drives average current flowing on at least one LED channel to be constantly maintained, and more particularly, to a light emitting device (LED) driving apparatus that controls channel current to be constantly maintained by feedbacking channel current flowing on a driven LED channel and a method for driving the LED.
2. Description of the Related Art
Generally, a display device using a cathode-ray tube (CRT) is disadvantageous in that its entire volume becomes larger and its weight and installation area are increased in order to enlarge a display region, causing inconvenience in portability.
In order to solve the problem of such a CRT, a flat panel display having a thinner thickness and a lighter weight than the CRT has been developed. As such a flat panel display, there are a liquid crystal display (LCD), a plasma display panel (PDP), etc.
The LCD is generally configured of a liquid crystal panel and a backlight unit. As a lamp used in such a backlight unit, a cold cathode fluorescent lamp (CCFL) has been mainly used but owing to the limitations in view of compactization, thinning, and light-weighting, a light emitting diode (LED) which is advantageous in view of power consumption, weight, brightness, etc., has been proposed.
The backlight unit of the liquid crystal display panel uses a plurality of light emitting diodes which are connected in series as a light source and in this case, each light emitting diode has forward voltage deviation so that there is a demand for a driving apparatus that drives the plurality of light emitting diodes connected in series using constant current.
FIG. 1 is a circuit view of a LED driving apparatus in the related art.
Referring to FIG. 1, the LED driving apparatus according to the related art includes a LED light source unit 10, channel voltage detectors 20a to 20n, a channel current controller 30, and a driver 40.
Generally, each LED element is designed to have the same forward voltage, but differences occur in the forward voltage due to errors generated during a product manufacturing process. Therefore, there are also differences in voltage values detected from the low ends of the plurality of LED channels 10a to 10n. 
The driver 40 uses a method to control boost voltage by comparing voltage measured from the low ends of the respective LED channels 10a to 10n with a reference potential in order to constantly adjust the voltage values in the low ends of the LED channels 10a to 10n measured from the channel voltage detectors 20a to 20n. 
Moreover, the channel current controller 30 controls the average current flowing on the respective channels to be constantly maintained through a linear scheme. A transistor connected to the low ends of the channels is operated in an active region, such that the linear control method has a problem of heat generation as much as obtained by multiplying the voltage applied across the transistor by the current.